Compositions comprising a polymer of acrylamide and an ether



United States Patent COMPOSITIONS COMPRISING A POLYMER OF ACRYLAMIDE AND AN ETHER Henry Z. Friedlander, Greenwich, and William A. Barber, Stamford, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application June 22, 1954,

Serial No. 438,603

11 Claims. (Cl. 260-304) This invention relates to new and useful compositions of matter and more particularly to compositions comprismg an acrylamide polymerization product and an ether selected from the class consisting of dioxolane and morpholine (including mixtures of dioxolane and morpholine in any proportions).

The compositions of this invention in which dioxolane or morpholine, or a mixture of dioxolane and morpholine, is employed primarily as a solvent or swelling agent for the acrylamide polymerization product, in which case it constitutes a major proportion (more than 50% e. g.,

from 55 to 99% or more, by weight of the composition,

are particularly useful in the production of shaped articles therefrom, e. g., filaments, films, threads, rods, tubes and the like, or as coating, adhesive, laminating, impregnating, paper-treating, textile-treating compositions, etc., or as components of such compositions. An ether of the kind aforementioned also may be used primarily as a plasticizer for an acrylamide polymerization product, in which case it usually constitutes a minor proportion (less than 50%), e. g., from 0.5 to 45%, generally from 1 to 35 or 40%, by weight of the composition. If the product is used or intended for use in an application where waterinsolubility is important, it can be rendered water-insoluble by suitable treatment or modification, as by crosslinking with a' cross-linking agent, e. g., methylene-bisacrylamide, diallyl phthalate, etc.

Polymers and copolymers of acrylamide were known prior to our invention. Likewise it was known that homopolymeric acrylamide and many of the copolymers of acrylamide are soluble in water. However, to the best of our knowledge and belief it was not known prior to our invention that acrylamide polymerization products could be dissolved or swollen in certain organic solvents. Thus, in a recent article by Shulz et al., Studies on the radical polymerization of acrylamide [Makromo]. Chem. 12, 20-34 (1954)], the authors state: The polyacrylamides prepared by the polymerization methods that we have described ble in ordinary solvents such as alcohols, esters, ethers, and hydrocarbons. Among the organic compounds spe- 'cifically mentioned by the authors as being non-solvents for polyacrylamide are tetrahydrofuran, dimethylformamide, nitrobenzene, bromobenzene and tetralin.

The present invention is based on our discovery that polymers and copolymers of acrylamide, more particularly polymeric (homopolymeric) acrylamide and thermoplastic copolymers of acrylamide, specifically such copolymers containing in their molecules an average of at least 75% by weight of combined acrylamide, e. g., copolymers of, by weight, from 75 to 99.5% of acrylamide and another monomer such, for instance, as vinyl acetate, methyl acrylate, ethyl acrylate, acrylic acid, etc., are compatible with dioxolane, morpholine and mixtures of dioxolane and morpholine, and that such ethers are capable of dissolving or swelling the acrylamide polymerization product to yield solutions or swollen masses which are suitable for use in a wide variety of industrial applications, examples of which have been given hereinbefore. The invention is based on our further discovery that the aforementioned ethers or mixtures thereof are able effectively to plasticize acrylamide polymerization products so that the latter more easily can be shaped, as by extrusion or molding, or cast into useful articles of manufacture. The ether employed in practicing our invention may be used either as a fugitive or temporary plasticizer, that is, a plasticizer which subsequently is removed from the polymerization product, or as a permanent plasticizer which is permitted to remain in the acrylamide homopolymer or copolymer.

are soluble in water, but insolu- The unobvious nature of our invention will be immediately apparent to those skilled in the art when it is considered that polyacrylamide does not dissolve upon being admixed with any of a large number of organic compounds, even when heated at C. for hour or when heated to boiling and then at boiling for about 10 minutes in the case of those compounds boiling under 120 C. Thus we have found that finely ground polyacrylamide does not dissolve, swell, or coalesce, when heated under the aforementioned conditions, in each of the following compounds:

Isoamyl alcohol Diethylene g l y c o l monoethyl ether Cresol Diethylene glycol Cyclohexanol Tetrahydrofurfuryl alcohol Ethylene glycol monoethyl ether Monoethylene glycol monoethyl formal Methacrylic acid Butyrolactone Pyrrolidone 2-methyldioxolane Dioxane Sulfolane Nitroethane Ethylene carbonate Ethylene sulfite Diallyl carbamate Triallyl cyanurate Acetic anhydride Chloromaleic anhydride Maleic anhydride Methyl ethyl ketone Homopolymeric acrylamide and acrylamide copolymers (thermoplastic acrylamide copolymers) containing in the polymer molecules an average of at least 75 by weight of combined acrylamide are employed in carrymg the present invention into effect. These polymers and copolymers are prepared by methods now well known to those skilled in the art. In some cases the polymerization rates of the individual monomers in a polymerizable mixture may be different, with the result that the proportions of the components in the final copolymer are different from the proportions thereof in the mixture of monomers which are polymerized. The proportions of monomers in the polymerizable mixture therefore are preferably adjusted, in practicing the present invention, so that the final copolymer contains in the molecules thereof an average of at least 75 by weight of combined acrylamide. The acrylamide polymerization product may be one in which, for example, a homopolymer of acrylamide has been modified by introducing one or more other groups into the polymer molecule. For example, the acrylamide polymerization product may be one in which homopolymeric acrylamide or certain copolymers of acrylamide have been hydrolyzed under acid or alkaline conditions to introduce carboxylic acid or salt groups into the polymer molecule or structure, or has been reacted with an aldehyde, specifically formaldehyde, to introduce alkylol, more particularly methylol, groups into the polymer structure. In such instances, the extent of hydrolysis or alkylolation or other modification is so controlled that the acrylamide polymerization product still contains at least 75% by weight of acrylamide units. The expression polymerization product containing in the polymer molecules an average of at least 75% by weight of combined acrylamide, as used herein and in the appended claims, means, therefore, a polymerization product (polymer, copolymer or interpolymer, graft polymer, or polymer modified by the introduction of other groups, etc., or mixtures thereof) containing in the molecules thereof an average of at least 75% by weight of the acrylamide unit, which is considered to be present in the individual polymer molecule as the group I CHr-JJH-l) O N112 or, otherwise stated, at least 75% by weight of the reactant substance converted into and forming or comprising' the polymerization product is acrylamide.

Illustrative examples of monomers which may be copolymerized with acrylamide to yield a polymerization product containing in the polymer molecules an average of at least 75% by weight of combined acrylamide are compounds containing a single CH2=C grouping, for instance, the vinyl esters and especially the vinyl esters of saturated aliphatic monocarboxylic acids, e. g., vinyl acetate, vinyl propionate, vinyl butyrate, etc.; vinyl and vinylidene halides, e. g., the vinyl and vinylidene chlorides, bromides and fluorides; allyl-type alcohols, e. g., allyl alcohol, methallyl alcohol, ethallyl alcohol, etc.; allyl, methallyl and other unsaturated monohydric acohol esters of monobasic acids, e. g., allyl and methallyl acetates, laurates, cyanides, etc.; acrylic and alkacrylic acids (e. g., methacrylic, ethacrylic, etc.) and esters and amides of such acids other than acrylamide (e. g., methyl, ethyl, propyl, butyl, etc., acrylates and methacrylates, methacrylamide, N-methyl, -ethyl, -propyl, -butyl, etc., acrylamides and methacrylamides, etc.); methacrylonitrile,

ethacrylonitrile and other hydrocarbon-substituted acrylonitriles; unsaturated aliphatic hydrocarbons containing a single CH2=C grouping, e. g., isobutylene, etc.; and numerous other vinyl, acrylic and other compounds containing a single CH2=C grouping which are copolymerizable with acrylamide to yield thermoplastic copolymers. Alpha,beta-unsaturated polycarboxylic acids and alkyl esters thereof also may be copolymerized with acrylamide to form copolymers which are useful in practicing the present invention, e. g., maleic, fumaric, citraconic, itaconic, etc., acids, and the dimethyl, -ethyl, -propyl, -butyl, etc., esters thereof.

The polymeric and copolymeric acrylamides used in practicing our invention may be of any suitable molecular weight, but ordinarily the molecular weight (weight average molecular weight) is not less than 10,000 and may be as high as 2 million or more. Ordinarily the weight average molecular weight is within the range of about 70,000 or 80,000 to 1,600,000-2,000,000. Such molecular weights (weight average molecular weights) are determined in the manner described more fully by P. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953, Chap. 7, p. 266 et seq. Briefly described the values are ascertained by calculating intrinsic viscosities (limiting viscosity numbers) from measurements of flow times in an Ostwald viscosimeter at 300 C. of any four concentrations of the acrylamide polymerization product below 0.5 g./l() ml. in water or 1 N sodium nitrate solution. The relation between the intrinsic viscosity and the weight average molecular weight is previously established by light-scattering measurements on a set of eight samples of pure polyacrylamide, in water, ranging in weight average molecular weight from 78,700 to 1,640,- 000. The light-scattering measurements are performed on solutions filtered through ultrafine sintered glass and are interpreted by standard light-scattering procedures and corrected by determinations of dissymmetries and depolarization ratios.

The dissolution of the acrylamide polymerization product in, or swelling by, the ether employed in practicing the present invention is accelerated by using a polymer or copolymer of acrylamide which is in a finely divided state, e. g., one which, if not in a finely divided state as originally formed, has been ground so that all or substantially all of it will pass through a U. S. Standard Sieve Series No. 50 screen. It also is usually desirable to agitate the mass, as by mechanical stirring, while admixing the polymerization product with the solvent. To avoid or minimize discoloration of the polymeric or copolymeric acrylamide, it is generally advantageous to employ the lowest possible temperature in effecting dissolution, swelling, or plasticization of the acrylamide polymerization product, which temperature is consistent with practical considerations, e. g., the time required for effecting solution (or other desired result), etc.

The proportions of the acrylamide polymerization product and ether in the compositions of our invention may be varied widely, depending mainly upon the particular use for which the composition is intended. If the ether (dioxolane, morpholine or a mixture of dioxolane and morpholine) is employed primarily as a solvent for the acrylamide homopolymer or copolymer so as to obtain, for example, a film or other shaped article, or to make a coating, impregnating, laminating, adhesive, textile-treating composition, etc., from which all or substantially all of the solvent subsequently is removed, them the acrylamide polymerization product usually constitutes at least 1%, but less than 50%, e. g., from 5% to about or by weight of the composition. Advantageously, in most cases, when the solution is to be used in, for example, the casting of films, the polymer or copolymer of acrylamide constitutes at least 5% by weight of the solution.

If the ether is to be employed primarily as a plasticizer for the acrylamide polymerization product, then the ether generally constitutes less than 50%, e. g., from 1% to or by weight of the composition (ether plus polymer or copolymer of acrylamide).

The aforementioned ranges of proportions are mentioned as indicative of proportions that may be employed in forming solutions of, or plasticized compositions containing, the acrylamide polymerization product, and our invention obviously is not limited to the use of only such proportions. The important factor is that the proportions be such that the viscosity or plasticity of the composition at the particular operating temperature (that is, the temperature at which the composition is employed) be within a workable range for the particular use to which the composition is to be placed.

In order that those skilled in the art may better understand how the present invention can be carried into effect, the following examples are given by way of illustration and not by way of limitation. All parts and percentages are by weight.

Example 1 One (1) part of dry homopolymeric acrylamide, ground so that substantially all of it passes through a U. S. Standard Sieve Series No. screen, is thoroughly mixed with 99 parts of morpholine. (The polyacrylamide employed has a weight average molecular weight of about 200,000 as determined by the method hereinbefore described, that is, by viscometric data related to previous light-scattering measurements.) The mixture is allowed to stand at room temperature (about 2030 C.) for 3 days, is thereafter heated to C. for 30 minutes, then is allowed to stand at room temperature for about one month, and finally is heated to 120 C. to obtain an opaque, plastic solid comprising swollen or gelled polyacrylamide. This material can be sheeted on rolls to form sheets of a desired thickness or can be extruded through slots to form films. The morpholine, in whole or in part (as may be desired), can be removed from the resulting sheet or film, as by heating or by solvent extraction, or from the sheet or film during its formation. For example, plasticized homopolymeric acrylamide is obtained by allowing a suitable amount of the morpholine to remain in the composition, for example from 1 or 2% to 35 or 40% or more by weight of the composition.

If water-resistant films or sheets are desired, they can beobtained by immersing the film or sheet (before or after removal of all or part of the morpholine) in an aqueous solution of formaldehyde to form the N-methylol derivative of the polyacrylamide, followed by heating at 120-150 C. to obtain a water-insoluble, cross-linked material.

Example 2 Example 1 is repeated with the exception that 1 part of dioxolane is substituted for 1 part of morpholine. Similar results are obtained.

Example 3 Same as in Example 1 with the exception that 1 part of a dry, ground copolymer of about acrylamide and 10% acrylic acid is used in place of the homopolymeric acrylamide. Similar results are obtained.

Example 4 Same as in Example 2 with the exception that 1 part of a dry, ground copolymer of about 90% acrylamide and 10% acrylic acid is used in place of the homopolymeric acrylamide. Similar results are obtained.

Example 5 One (1) part of dry, ground homopolymeric acrylamide such as was employed in Example 1 and 99 parts of a mixture of 75% commercial grade formamide and 25% morpholine are well mixed and then allowed to stand at room temperature for 3 days, at the end of which period of time the polymer has substantially completely dissolved.

When another sample of the same mixture is heated for 30 minutes at C., partial solution of the polymer is obtained, and complete solution after further heating at the same temperature.

combined acrylamide.

Use of a solvent mixture of 75% formamide and 25% dioxolane produces the same results as a solvent mixture of 75% formamide and 25% morpholine.

Example 6 Same as in Example 5 with the exception that there is employed a dry, finely divided copolymer of about 75% acrylamide and 25 of (a) vinyl acetate, or (b) methyl acrylate, or (c) styrene, or (d) methacrylonitrile, or (e) methacrylamide. Similar results are obtained.

Instead of the morpholine or the dioxolane employed in the foregoing illustrative examples, one can use mixtures of morpholine and dioxolane in any proportions, for instance equal parts by weight of morpholine and dioxolane.

It will be understood, of course, by those skilled in the art that our invention is not limited to the specific ingredients and method of effecting solution of the polymer or copolymer of acrylamide that are given by way of illustration in the foregoing examples. Thus, instead of the specific comonomers employed in Examples 4 and 6 in forming copolymers with acrylamide, we may use any other comonomer which is copolymerizable with acrylamide in the proportions hereinbefore set forth, that is, in proportions such that the finished copolymer contains in the molecules thereof at least 75 by weight of Numerous examples of such comonomers were given previously in the specification.

The advantages of the present invention will be immediately apparent to those skilled in the art from the foregoing description. The invention broadens the field of utility of polyacrylamide, since it provides solvents and plasticizers therefor, other than water, and thus makes the resulting compositions suitable in applications for which aqueous solutions of polyacrylamide would be entirely unsuited. As is well known, aqueous solutions of polyacrylamide are polar and have a high dielectric constant; consequently such solutions are entirely unsuitable for many applications.

As a result of the present invention all of the inherent advantages of a non-aqueous solvent or swelling agent can be utilized in working with the polyacrylamide (homopolymeric acrylamide) and with copolymers of acrylamide containing at least about 75 of acrylamide combined in the polymer molecule. For instance, the invention provides compositions which can be extruded or otherwise shaped to form useful articles of manufacture. The compositions of the present invention are also useful in warpsizing and other textile-treating applications, as well as in adhesive compositions, ceramic binders, nitrocellulose lacquers, as components of rubber-based glues, in furniture glues which are capable of withstanding freeze-thaw cycles, in making chemical analyses of polymers and copolymers of acrylamide where it is desired to make the analysis in a non-aqueous solvent for the acrylamide polymerization product, and for various other purposes, many examples of which have been given hereinbefore.

We claim:

1. A composition of matter comprising (1) a polymerization product containing in the polymer molecules an average of at least 75 by weight of combined acrylamide molecules thereof, an average of at least 75 by weight of acrylamide and an average of up to 25% by weight of a different compound containing a CH2==C grouping.

4. A composition as in claim 1 wherein the polymerization product of (1) constitutes at least 1% by weight of the composition.

5. A composition of matter comprising l) a polymerization product containing in the polymer molecules an average of at least by weight of combined acrylamide and (2) dioxolane.

6. A composition of matter comprising 1) a polymerization product containing in the polymer molecules an average of at least 75 by weight of combined acrylamide and (2) morpholine.

7. A composition of matter comprising (1) a polymerization product containing in the polymer molecules an average of at least 75% by weight of combined acrylamide and (2) dioxolane, the polymerization product of (1) constituting from about 5% to about 30%, by weight, of the total amount of (1) and (2).

8. A composition of matter comprising (1) a polymerization product containing in the polymer molecules an average of at least 75 by weight of combined acrylamide and (2) morpholine, the polymerization product of (1) constituting from about 5% to about 30%, by weight, of the total amount of (1) and (2).

9. A plasticized composition comprising a polymerization product containing in the polymer molecules an average of at least 75% by weight of combined acrylamide, said polymerization product being plasticized with a plasticizing amount not substantially exceeding 40% by weight of the compostiion of a plasticizer comprising an ether selected from the class consisting of dioxolane and morpholine.

10. A composition comprising a plasticized polymerization product containing in the polymer molecules an average of at least 75 by weight of combined acrylamide, said polymerization product being plasticized with from about 1% to about 35% by weight of the whole of dioxolane.

11. A composition comprising a plasticized polymerization product containing in the polymer molecules an aver age of at least 75 by weight of combined acrylamide, said polymerization product being plasticized with from about 1% to about 35% by weight of the whole of morpholine.

References Cited in the file of this patent UNITED STATES PATENTS 2,340,907 Sussman et a1. Feb. 8, 1944 

1. A COMPOSITION OF MATTER COMPRISING (1) A POLYMERIZATION PRODUCT CONTAINING IN THE POLYMER MOLECULES AN AVERAGE OF AT LEAST 75% BY WEIGHT OF COMBINED ACRYLAMIDE AND (2) AN ETHER SELECTED FROM THE CLASS CONSISTING OF DIOXOLANE AND MORPHOLINE. 